UPSC Civil Services exam is conducted in three parts - preliminary, mains and interview.
After preliminary, the cut off for appearing in mains is announced. Those who have got below that are not entitled to appear for mains. For example last year (2017) this cut off score was 105.3 for general category candidates.
These cut off vary year to year, though not significantly and depend on many factors like - total number of vacancies, total number of candidates participating, level of difficulty of questions etc.
After mains exam it's cut off is announced based on which candidates are called for interview.
The final cut off are announced after the result of interview which determines the finally selected candidates.
So practically 3 cut offs are announced time to time. The cut offs will vary from category to category also.
As a typical example the cut offs for the year 2016 for general, OBC and SC categories were -
Prelim ---- 116, 110.66, 99.34
Mains ----- 787, 745, 739
Final ------ 988, 951, 937
You can expect the future cut offs also in line with them but always be prepared for the surprises so you have to put the maximum efforts possible and forget about the cut offs. These cut offs are only a guideline, they are not the benchmarks.
Knowledge is power.